I own a 1988 Buick LeSabre which has 104,000 miles on it. It runs great and I am very satisfied with its performance. The mechanic who does my repairs recently sent me a postcard telling me that after 100,000 miles, I'm due for a new timing chain. The cost would be $700. Should I do it? -- David

TOM: Was the postcard from Cancun? Maybe he got the postcard idea from his dentist. Were the words "oral exam" crossed out and the words "timing chain" written in over them?

RAY: Timing BELTS need to be changed as preventive maintenance every 60,000 miles or so. But timing CHAINS, which is what your car has, generally don't get changed at all until they break or get noisy. And most timing chains last well over 100,000 miles. In fact, if you drive gently, it's unlikely you'll ever need to replace the timing chain on this car, David.

TOM: So I would say it's totally unnecessary. If your timing chain starts making a rapping noise at some point, and some other, less "enthusiastic" mechanic confirms that the noise is coming from the timing chain, then you can go ahead and replace it. But until then, I'd just tear up the postcard and keep driving.

RAY: And by the way, if you should decide at some point that it's time for a new mechanic, you can always search our reader/listener database of "recommended" mechanics on our web site "http: //cartalk.com." Just check the table of contents for the "Mechan-X-Files."